A guy (normally) who is so offensive, rude, self centered, selfish, self serving, mean, insensitive, lacking is social skills, and clueless about what a unpleasant person he is to be around that once anyone else gets to know him, or his rep gets spread around, the closest thing he can get to sex, intimacy, pussy, ass, a kiss, a grope, the scent of perfume a lá femme -- or even another guy's dick for that matter -- is jerking off and imagining it. An exceptional jerk actually sees jerking as the best way to have sex because it's impossible for him to get sex from a woman (or even another dude).
Some guys (who may have been the shit motherfuckers when they were young) never realize they are jerks even when they have greying scragly mpb (male pattern baldness), can't remember what their cock looks like because they can't see past their beer gut, and they need to pay for skanky sex with toothless hookers.
The female equivalent would probably be the word "cunt." But both terms can be applied to either gender, often with greater effect and meaning. If a guy's a cunt, why would girls want to have sex with him (chicks like dick)? Fags especially want nothing to do with a cunt. A jerk can only dream of cunt. A girl who's "a dick" can't get guys or even lesbians.
Don't even say hello to him, he's a jerk. If he walks over, let's leave.
You're such a jerk you can't even get a blowjob in a gay bath house.
I'm such a jerk, I think my dick is the only thing that will ever love me. I dream of pussy. Queers don't even want to suck me off. I'm all alone.